Valves of Encyonopsis dakotae are larger and have a larger central area and lower stria density. Encyonopsis medicinalis valves are smaller and elliptic-lanceolate in shape. Encyonopsis descripta and E. descriptiformis have large, rounded central areas. Encyonopsis descriptiformis also has rostrate to short, apiculate apices. Encyonopsis descripta var. asymmetrica has a larger central area and lower stria density.